Electric blasting cap



M 3 G. A. NODDIN ELECTRIC BLASTING CAP Filed Aug. 13, 1930 760L7EA NOdO I I), Invenror Patented May 2, 1933 v UNl TED STATES PATENT OFFICE GEORGE A. NODDIN, OIlS POMPTON LAKES, NEW JERs EY, ASSIGNOR TO EQI. DU PONT DE mmouns 8. COMPANY, on

WILMINGTON, DELAWARE, A .GORP OBATION OF DELA- ELECTRIC BLASTING CAP Application filed August 13, 1930. "serial No. 474,980.

This invention relates to electric blasting caps, and more particularly to an-improved lead azide primed electric blasting cap, and comprises essentially the manufacture of such a cap without the use of a pressed binding and ignition charge for lead azide heretofore required.

It has long been recognized that lead azide possesses certain advantages over mercury fulminate as a primer in composition blasting caps; firstly, it is fundamentally cheaper to produce than mercury ful1ninate;secondly, ess of it is required to detonate a given secondary detonating compound; thirdly, it. is certain in action even without an inner capsule, whereas fulminate in reasonable amounts is certain only with a capsule; fourthly, it cannot be dead pressed within the ranges of pressure ordinarily considered for blasting caps; fifthly, it is less affected by moisture. However, it has been recognized as well that lead azide possesses at least two inherent disadvantages; the outstanding disadvantages are, one, that it is less easily ignited than mercury fulminate; and, two, that it does not bind .as satisfactorily in cap shells. Because of these disadvantages all lead azide primed blasting caps which have been successfully manufactured and market ed. have contained, either mixed with the lead azide or superimposed upon it, a'"material which, when pressed into the cap shell, has possessed satisfactory ignition and binding qualities. Numerous compounds and mixtures have been used for this purpose, as for example the /normal or basic salts of styphnic and picric acids, particularly, and in some cases mixtures of mercury fulminate with oxidizing compounds and the like and mixtures of sulphocyanate and oxidizing compounds, either with or without an added low flash point fuel.

Electric blasting caps containing lead azide as a priming charge have likewise been provided with one of these igniting and binding agents. These electric detonators have usually been ignited by either of two general methods; one, a so called match head in which 'a wire is surrounded by a mass or bulk of ignitable material, and two, ,a bridge wire bridge.

embedded in a loose charge of ignitable material. In both cases the ignition is eflected by heat generated in the bridgewire by passage of electric current from an outside source through leading wires attached to said this latter composition having the advantages of those previously used, of low cost, satisfactory compatibility with all materials commonly used for blasting cap shells, and high resistance to moisture. One of the objects of my invention is to simplify the manufacture of electric.blast ing caps. Another object of my invention is to improve generally upon the manufacture of blasting caps. further object of my invention is to provide an electric blasting cap which may be manufactured at lower cost than those heretofore produced.

By using in a lead azide primed electric blasting cap, a loose charge containing a. sulphocyanate, an'oxidi'zing agent, and a low flash point fuel for igniting the same I have For a loose charge, to which this I invention relates, there has been used for the discovered that a satisfactory electric-blasting cap can be produced without the use of an igniting and binding agent with the lead azide priming charge. I have found that the heat supplied by the above preferred loose ignition charge'is wholly adequate to ignite pressed lead azide without failure. Furthermore, I have found that no binding agent is necessary with the lead azide charge provided the electric detonator contains above the lead azide charge a loose charge of ignition materialwhich is held in place by the usual means of holding the bridge wire, as for example, by a sulphur plug.

By this means the ignition compound or- In the drawing a represents a metallic shell.

This may be of gilding metal, brass, copper, nickel, aluminum.-steel or any other of the .other metals ordinarily considered satisfactory for blasting cap shells. Letter 6 refers to a charge of a secondary detonating compound which, for example, may comprise tetranitromethyaniline (tetryl) pentaerythrite tetranitrate, erythrite tetranitrate, trinitrotoluene, picric acid or mixtures of these materials. The letter 0 designates a pressed charge of lead azide. The letter (Z represents a loose charge of ignition mate rial preferably a composition comprising asulphocyanate an oxidizing agent, and a low flash point fuel. In this composition I prefer to use that disclosed in the copending applications of H. A. Lewis, one of which has resulted in U. S. Patent 1.797509, and the other of which is Serial No. 474,016, filed August 8, 1930, in which lead sulphocyanate, potassium chlorate, and ground Pyro powder have beenshown to be satisfactory as a sulphocyanate. an oxidizing agent, and ya low flash point fuel respectively. In the drawing the letter 6 refers to a bridge wire, 7 to leading wiresattached to said bridge, 9 a sulphur plug'through which the leading wires pass. It a-charge of waterproofing material, ancLi acharge of sulphur as sealing agent.

It will be understood of course that my invention is applicable not only to the above preferred embodiment, but may also be used in the several types of lead azide pruned electric blasting caps. and that I do not Intend to be limited in my invention except as indicated in the following patent claims.

I claim:

1. A lead azide primed electric blasting cap having a loose ignition composition above the lead azide charge free of a pressed ignition charge.

2. A lead azide primed electric blasting cap having above the lead azide charge aloose charge of a composition comprising a sulphoc-yanate. an oxidizing agent. and a low flash point fuel. and free of a pressed ignition composition either mixed with-or superimposed upon said lead azide.

3. A lead azide primed electric blasting cap having above the lead azide charge a loose charge of a composition comprising lead sulphocyanate, potassiumchlorate and ground pyro powder, and free of a pressed ignition composition either mixed with or superimposed upon the said lead azide.

4. A lead azide primed electric blasting cap having above the'lead azide charge a loose charge of, a composition comprising 30-50% lead sulphocyanate, 10-30% potassium chlorate and 30-50% ground pyro powder and free of a pressed ignition composi- 7 6. An electric blasting cap comprising a metal shell. a charge of a secondary detonating compound. a pressed charge of lead azide,

a loose charge of an ignition composition consisting of lead sulphocyanate, potassium chlorate. and ground pyro powder, said blasting cap being free of a pressed ignition charge and having a bridge wire attached to current leading wires embedded in said loose charge.

7. An electric blasting cap comprising a metal shell. a charge of a secondary detonating compound. a pressed charge of lead azide, a. loose charge of an ignition composition consisting of 30-50% lead sulphocyanate, 10-30% potassium chlorate, and 30-50% ground pyro powder. said blasting cap being free of a pressed ignition charge and having a bridge wire attached to current leading wires embedded in said loose charge.

. 8. An electric blasting cap comprising a metal shell, a pressed charge of tetryl, a pressed charge of lead azide. and a loose charge of an ignition composition consisting of a sulphocyanate. an oxidizing agent and, a low flash point fuel. said blasting cap being free of'apressed ignition charge and having a bridge wire attached to current leading I wires embedded in said loose charge.

'9. An electric blasting cap comprising a metal shell, a pressed charge of tetryl, a pressed charge of lead azide. and a loose charge of an igition composition consisting of lead sulphocyanate. potassium ,chlorate, and ground pyro powder, said blasting cap being free of a pressed ignition charge and having a bridge wire attached to current leading wires embedded in said loose charge.

10. An electric blasting cap comprising a metalshell, a pressed charge of tetryl, a pressed charge of lead azide, and a loose charge of an ignition composition consisting of 30-50% lead sulphocyanate, 10-30% potassium chlorate, and 30-50% ground pyro powder, said blasting cap being free of a pressed ignition charge and having a bridge wire attached to current leading wires embedded in said loose charge.

In testimony whereof I 'aflix my signature.

GEORGE A. NODDIN. 

